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SPI 6.5
Predict the types of tides that occur when the Earth and the moon occupy various positions
TidesTides are daily movements of ocean water
that change the level of the ocean’s surface.
TidesTides are influenced by the sun and the
moon, and they occur in a variety of cycles.
The Lure of the MoonThe gravity of the moon pulls on every particle of
the Earth.
The Lure of the MoonThe pull is much more
noticeable in liquids than in solids because liquids
move more easily.
The Lure of the Moon
Even the liquid in an open soft drink is slightly pulled by the moon’s gravity.
The Lure of the MoonGravitational forces from both the sun and
the moon continuously pull on the Earth.
The Lure of the MoonAlthough the moon is much smaller than the sun, the
moon’s gravity is the dominant force behind
Earth’s tides.
High and Low TidesHow high tides get and how often they occur
depend on the position of the moon as it revolves
around the Earth.
High and Low TidesThe moon’s pull is strongest on the part of the Earth
directly facing the moon.
High Tides vs. Low Tides
Because of inertia, water wants to fly off of earth, but is balanced by gravity. The water that is directly facing the moon gets
pulled (bulges) from the gravitational pull of the moon causing a high tide.
High Tides vs. Low Tides
The side directly opposite also experiences a hightide because as the moon is pulling the other side it throws off the earth’s center of gravity, causing more of a gravitational pull to be on the side with
the moon. Thus the effects of inertia on the opposite side become greater because there is less
of a gravitational pull. Here you also get a high tide.
High Tides vs. Low Tides
When high tides occur, water is drawn away from the area between the high tides, causing low tides to form.
High Tides vs. Low Tides
Copy this diagram into your notes in the space provided.
High Tides vs. Low Tides
Bay of Fundy at high tide Bay of Fundy at low tide
http://www.howitworksdaily.com/environment/bay-of-fundy-time-lapse/
http://www.youtube.com/watch?v=OP0cpXpw8yk
High Tide and Low Tide
Timing the TidesTides occur at differentspots on Earth because the Earth rotates more quickly than the moonrevolves around the Earth.
Tidal VariationsThe sun also affects tides.
The sun is much larger than the moon, but it is also much farther away.
Tidal VariationsAs a result, the sun’s influence on tides is less
powerful than the moon’s influence.The combined forces of the sun and the moon on the Earth result in tidal ranges that vary based on the positions of all three bodies.
Spring TidesWhen the sun, Earth,
and moon are in alignment with one another, spring tides
occur.
Spring TidesSpring tides are tides with maximum daily
tidal range that occur during the new and
full moons.
Neap TidesWhen the sun,
Earth, and moon form a 90° angle, neap tides occur.
Neap TidesNeap tides are tides
with minimum daily tidal range that occur during
the first and third quarters of the moon.
Neap TidesThe gravitational
forces on the Earth by the sun and the moon work against
each other.
Neap and Spring Tides
Tides and TopographyTides can be accurately predicted
once the tidal range has been measured at a certain point over
a period of time.
It’s a good thing that people on the beach knew when high tide
occurred.
Tides and TopographyThese photos show the Bay of Fundy, in New Brunswick, Canada.
The Bay of Fundy has the greatest tidal range on
Earth.